WO2021249175A1

WO2021249175A1 - Auxiliary wafer, preparation method therefor and semiconductor manufacturing process

Info

Publication number: WO2021249175A1
Application number: PCT/CN2021/095595
Authority: WO
Inventors: 郭帅
Original assignee: 长鑫存储技术有限公司
Priority date: 2020-06-08
Filing date: 2021-05-24
Publication date: 2021-12-16
Also published as: CN113838743A

Abstract

Provided are an auxiliary wafer, a preparation method therefor and a semiconductor manufacturing process. The method for preparing an auxiliary wafer comprises: providing an initial wafer (100); forming a protective film (110) on the surface of the initial wafer (100), wherein the material of the protective film (110) comprises an alumina in a low temperature phase; and subjecting the protective film (110) to an annealing process, so that at least part of the alumina is transformed from the low temperature phase into a high temperature phase, so as to form a protective layer (120).

Description

Auxiliary wafer and its preparation method and semiconductor manufacturing process

cross reference

This application claims the priority of the Chinese patent application titled "Auxiliary Wafer and Its Preparation Method, Semiconductor Manufacturing Process" and the application number is 2020105136501 filed on June 8, 2020, which is fully incorporated into this application by reference.

Technical field

The embodiments of the present application relate to the field of semiconductors, and in particular, to an auxiliary wafer, a preparation method thereof, and a semiconductor manufacturing process.

Background technique

In the machine process, in order to monitor the wafer process, it is usually necessary to use auxiliary wafers to monitor or maintain the effectiveness of the process. The same product process is performed on the auxiliary wafer and the surface of the product wafer. In order to make the auxiliary wafer recyclable, the auxiliary wafer is usually pre-processed before the auxiliary wafer is placed in the machine. A protective film is formed on the surface of the wafer to be processed. The protective film can protect the auxiliary wafer when removing other materials on the side of the protective film away from the auxiliary wafer to avoid damage to the auxiliary wafer caused by the removal process, thereby ensuring the auxiliary wafer Can be recycled.

The existing protective film has poor durability, is easy to be damaged, the auxiliary wafer has a limited lifespan, has a small number of cycles, and the semiconductor manufacturing process cost is relatively high.

Summary of the invention

Some embodiments of the present application provide an auxiliary wafer, a preparation method thereof, and a semiconductor manufacturing process, which are beneficial to increase the number of times the auxiliary wafer can be recycled.

In order to solve the above problems, some embodiments of the present application provide a method for preparing an auxiliary wafer, including: providing an initial wafer; forming a protective film on the surface of the initial wafer, and the material of the protective film includes low-temperature alumina Perform an annealing process on the protective film, so that at least part of the aluminum oxide is transformed from the low-temperature phase to the high-temperature phase to form a protective layer.

In addition, the forming a protective film on the surface of the initial wafer includes: forming the protective film on the surface of the initial wafer using a precursor, the precursor including trimethylaluminum and ozone, or the precursor Substances include aluminum trichloride and ozone.

In addition, a carrier gas is used to carry the trimethylaluminum, and the flow rate of the carrier gas is 100 sccm to 400 sccm.

In addition, the protective film is formed using the precursor under the temperature condition of 200°C to 600°C.

In addition, the annealing process includes spike annealing, and the annealing temperature of the spike annealing is greater than 900°C.

In addition, the high-temperature phase alumina includes α-alumina.

In addition, the method for forming the auxiliary wafer further includes: forming a functional layer on the protective layer, and the etching selection ratio of the functional layer and the initial wafer in the same etching process is smaller than that of the functional layer and the initial wafer. The etching selection ratio of the protective layer.

Correspondingly, some embodiments of the present application also provide an auxiliary wafer, including: an initial wafer and a protective layer on the surface of the initial wafer, the material of the protective layer includes alumina, and the aluminum oxide The phase includes the high temperature phase.

In addition, in a direction perpendicular to the surface of the initial wafer, the thickness of the protective layer is greater than or equal to 2 nm.

In addition, the material of the protective layer includes α-alumina.

Correspondingly, some embodiments of the present application also provide a semiconductor manufacturing process, including: providing a product wafer and the above-mentioned auxiliary wafer; Step A: performing the same process on the product wafer and the auxiliary wafer, so as to A functional layer is formed on the surface of the product wafer and the auxiliary wafer; step B: removing the functional layer on the surface of the auxiliary wafer.

In addition, the step A and the step B are executed cyclically.

Compared with the prior art, the technical solutions provided by some embodiments of this application have the following advantages:

In the above technical solution, the alumina has a more stable crystal phase structure, higher hardness, and lower activity by transforming the alumina from a low temperature phase to a high temperature phase. This is beneficial in removing the surface of the auxiliary wafer. In the case of dielectric materials, it reduces the damage to alumina caused by the removal process, increases the recyclable number of auxiliary wafers, and effectively reduces the cost of the semiconductor manufacturing process.

In addition, compared to the uniform temperature annealing, the use of spike annealing is beneficial to shorten the annealing time, and can also better remove the water molecules in the low-temperature phase alumina.

Description of the drawings

One or more embodiments are exemplified by the pictures in the corresponding drawings. These exemplified descriptions do not constitute a limitation on the embodiments. The elements with the same reference numerals in the drawings are denoted as similar elements. Unless otherwise stated, the figures in the attached drawings do not constitute a scale limitation.

1 and 2 are schematic cross-sectional structural diagrams corresponding to each step of a method for forming an auxiliary wafer according to an application embodiment;

3 to 4 are schematic diagrams of cross-sectional structures corresponding to various steps of a semiconductor manufacturing process according to an embodiment of the application.

detailed description

In the semiconductor industry, wafers used to monitor the process stability between batches are called control wafers, and wafers used to maintain the stability of a single batch process are called dummy wafers. The main function of the control plate is to monitor the stability and repeatability of the machine (including the furnace tube and the chamber machine) through the process; the main function of the baffle is to stabilize the airflow and balance the internal temperature of the machine by filling the vacant position , So as to maintain the stability and uniformity of the process.

Specifically, in the furnace control process, in order to monitor whether the furnace tube machine is stable, it is necessary to place the control sheet and the product wafer in the machine for the process to compare and observe the process quality; in addition, to maintain the airflow in the furnace tube The characteristics such as stable distribution are stable. When the number of product wafers in the furnace tube is insufficient, auxiliary wafers need to be added to supplement. When the chamber machine is warmed up, it is usually necessary to use a certain number of auxiliary wafers for operation.

The method for forming an auxiliary wafer provided by the implementation of this application uses low-temperature alumina as a raw material and is transformed into a high-temperature phase through an annealing process. Compared with low-temperature alumina, the high-temperature alumina High crystal structure stability and low reactivity, so it is helpful to avoid the reaction between alumina and the etchant in the removal process, reduce the damage caused by the etchant to the protective layer, and improve the recyclability of the protective layer frequency.

The auxiliary wafer in this application includes a control wafer (Control Wafer) and a dummy wafer (Dummy Wafer). The control wafer can be placed in the machine together with the product wafer for process processing, or it can be processed separately. It should be noted that although the baffle does not need to be processed, its surface still has the problem of being contaminated. The pollution sources include molecular contaminants carried by the heat flow during warming up. Therefore, the baffle needs to be cleaned after use. In order to avoid damage to the baffle plate caused by the cleaning process, a protective layer of a certain thickness can be formed on the surface of the baffle plate so that the baffle plate can be recycled.

In order to make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the various embodiments of the present application will be described in detail below in conjunction with the accompanying drawings. However, a person of ordinary skill in the art can understand that in each embodiment of the present application, many technical details are proposed for the reader to better understand the present application. However, even without these technical details and various changes and modifications based on the following embodiments, the technical solution claimed in this application can be realized.

1 and 2 are schematic diagrams of the cross-sectional structure corresponding to each step of a method for forming an auxiliary wafer provided by an application embodiment.

Referring to FIG. 1, a preliminary wafer 100 is provided, and a protective film 110 is formed on the surface of the preliminary wafer 100. The material of the protective film 110 includes low-temperature phase aluminum oxide.

In this embodiment, the initial wafer 100 has the same size as the product wafer. In this way, it is possible to directly use the product wafer processing to form the auxiliary wafer without preparing the initial wafer 100 separately, so that the initial wafer 100 is easier to obtain.

In other embodiments, the size of the initial wafer is adjusted according to the thickness of the protective layer to be formed, so that the size of the auxiliary wafer after the protective layer is formed is the same as the size of the product wafer. In this way, it is helpful to ensure that the size of the product structure formed on the surface of the auxiliary wafer is the same as the size of the product structure formed on the surface of the product wafer, so that the auxiliary wafer can more accurately monitor whether the product structure formed on the surface of the product wafer meets the requirements. Pre-determined requirements.

In this embodiment, a precursor is used to form the protective film 110 on the surface of the initial wafer 100, and the precursor includes trimethylaluminum and ozone; in other embodiments, the precursor includes aluminum trichloride and ozone.

For example, trimethylaluminum is carried by a carrier gas so that the trimethylaluminum can be sent into the reaction chamber together with ozone. Compared with solid trimethylaluminum, trimethylaluminum carried by carrier gas has a lower density and can fully react with gaseous ozone. In this way, it is beneficial to ensure the full utilization of the precursors. At the same time, since the trimethylaluminum is a toxic substance, the full reaction of the trimethylaluminum is beneficial to reduce the cost of subsequent pollution treatment, thereby reducing the overall process cost.

In this embodiment, the flow rate of the carrier gas is 100 sccm to 400 sccm, for example, 200 sccm, 250 sccm, or 300 sccm. The use of the carrier gas flow rate in this range is beneficial to ensure that the trimethylaluminum carried by the carrier gas can fully react with ozone, and there is little or no residue after the reaction; in addition, it is beneficial to avoid excessive trimethylaluminum and ozone. At the same time, the reaction releases excessive heat, thereby avoiding problems such as explosions that may be caused by excessive heat release, and improving the safety of the manufacturing process.

In this embodiment, when using the precursor to form the protective film 110, the temperature condition in the reaction chamber is controlled within 200°C to 600°C, for example, 300°C, 400°C, or 500°C. In this way, it is beneficial to avoid the trimethylaluminum explosion caused by excessively high temperature in the reaction chamber, and to ensure the safety of the manufacturing process; in addition, it is beneficial to dehydrate the initially formed alumina to a certain degree, so that its formation has a relatively stable Low-temperature phase alumina with crystal structure, such as ρ-AL2O3, χ-AL2O3, η-AL2O3 or γ-AL2O3, the molecular formula of low-temperature phase alumina can be written as AL2O3·nH20, where 0<n<0.6.

Because the low-temperature phase alumina shrinks to a certain extent during the annealing process, that is, the molecular group size of the high-temperature phase alumina is smaller than the molecular group size of the low-temperature phase alumina. Therefore, after the protective film 110 is converted into a protective layer, the protective layer The thickness in the direction perpendicular to the surface of the initial wafer 100 is smaller than the thickness of the protective film 110. That is, when the initial protective film 110 is formed, the thickness of the protective film 110 should be greater than the required thickness of the protective layer.

In this embodiment, the protective film 110 covers the entire surface of the initial wafer 100, for example, including the side and upper and lower surfaces of the initial wafer 100 to ensure the protective effect of the protective layer formed by annealing the protective film 110; in other embodiments In this case, the protective film covers part of the surface of the initial wafer, for example, it may only cover the upper surface.

Referring to FIG. 2, after the protective film 110 is formed (refer to FIG. 1 ), the protective film 110 is heat-treated using a spike annealing process to form the protective layer 120.

Compared with the uniform temperature annealing process, the peak annealing process has a shorter annealing time while realizing the effective dehydration of the low-temperature phase alumina, which is beneficial to shorten the process time. In this way, while the protective film 110 is transformed into the protective layer 120, the heat accumulated in the furnace tube and the reaction chamber can be reduced, and accidents such as combustion and explosion caused by excessive heat can be avoided.

In this embodiment, the peak temperature of the spike annealing process is greater than 900°C. In this way, it is beneficial to transform the aluminum oxide in the protective layer 120 into completely dehydrated α-AL2O3, commonly known as corundum. α-AL2O3 is the most stable type of aluminum oxide crystal structure found so far. It has hardness second only to diamond and is not easily damaged. It is insoluble in strong acids and can protect the initial wafer 100 better.

In this embodiment, after the protective layer 120 is formed, a functional layer is formed on the protective layer 120, for example, a structural layer or a material layer realized by deposition, etching, printing, etc. The same etching process affects the functional layer and the initial layer. The etching selection ratio of the wafer 100 is smaller than the etching selection ratio of the functional layer and the protective layer 120. In this way, it is beneficial to ensure the protective effect of the protective layer 120.

In this embodiment, the alumina has a more stable crystal phase structure and lower activity by transforming the alumina from a low-temperature phase to a high-temperature phase, so that it is beneficial to remove the dielectric material on the surface of the auxiliary wafer. To remove the damage of aluminum oxide caused by the process, for example, taking the monitoring wafer as an example, the Al2O3 after high temperature annealing is extremely resistant to corrosion by the mixed solution of hydrofluoric acid/nitric acid, and the etching rate is almost zero. When the number of recycling cycles is small, there is no need to perform pre-processes to form a protective layer, or even perform performance confirmation, and can be directly put into the furnace tube or reaction chamber to be used as a monitoring wafer again without annealing. Al2O3 or a dielectric material with a high dielectric constant can be corroded by a mixture of hydrofluoric acid/nitric acid at a high etching rate. After several recovery cycles, its performance needs to be confirmed to confirm that it is still Has better protection performance.

The above-mentioned solution can effectively increase the recyclable times of the protective layer and the auxiliary wafer. Compared with the ordinary recycle times of 10-30 times, the technical scheme described in this application can reach 300 times, which is effective. Reduce the cost of control wafers (Control Wafer, including monitoring wafers, filling wafers) and/or dummy wafers (DummyWafer).

Correspondingly, an embodiment of the present application also provides an auxiliary wafer, which can be made by using the above-mentioned auxiliary wafer forming method.

Referring to FIG. 2, the auxiliary wafer includes: an initial wafer 100 and a protective layer 120 on the surface of the initial wafer 100. The material of the protective layer 120 includes alumina, and the phase of the alumina includes a high-temperature phase.

In this embodiment, the protective layer 120 covers the entire surface of the initial wafer 100, for example, including the side, upper and lower surfaces of the initial wafer 100; in other embodiments, the protective layer covers part of the surface of the initial wafer, for example, it may only cover surface. When the protective layer 120 only covers the upper surface of the initial wafer 100, when the mixed acid is used for cleaning, the mixed acid will corrode the area of the initial wafer 100 that is not covered by the protective layer 120. However, compared with the existing Technology can still increase the number of recyclable auxiliary wafers.

In this embodiment, the material of the protective layer 120 at any position on the surface of the initial wafer 100 is high-temperature alumina; in other embodiments, there is only the protective layer on the upper surface of the initial wafer (that is, the surface where the process is performed) The material of is high-temperature phase alumina, and the material of the protective layer at the remaining positions is low-temperature phase alumina; or, the protective layer includes a first protective layer in contact with the surface of the initial wafer and a second protective layer away from the surface of the initial wafer. The material of one protective layer is low-temperature phase alumina, and the material of the second protective layer is high-temperature phase alumina.

In this embodiment, in the direction perpendicular to the surface of the initial wafer 100, the thickness of the protective layer 120 is greater than or equal to 2 nm. In this way, it is beneficial to make the protective layer 120 have a higher recyclable number of times. It should be noted that the cycle times of the protective layer 120 are not only related to the thickness of the protective layer 120, but also related to the process steps in the semiconductor manufacturing process. For example, in addition to the corrosion of the hydrofluoric and nitric acid mixture in the removal process, during other process steps, especially heat treatment steps, high temperatures will pass through the protective layer 120 and affect the performance of the initial wafer 100.

For example, when the initial wafer 100 contains conductive materials placed in the through-silicon vias, multiple heat treatments may cause the conductive material to expand and deform, thereby making the stress at various positions of the initial wafer 100 uneven, and even causing the initial crystal The circle 100 has deformed features such as cracks. Therefore, when considering the thickness of the protective layer 120, in addition to the process time of the annealing process (the long time may have the risk of explosion) and the required number of cycles, the durability of the initial wafer 100 also needs to be considered, that is, the initial crystal The number of processes that the circle 100 can go through ensures that the performance of the initial wafer 100 meets the requirements during the recycling cycle, thereby ensuring that the final functional layer test result is correct.

In this embodiment, the material of the protective layer 120 includes α-alumina, commonly known as corundum.

In this embodiment, high-temperature aluminum oxide is used as the protective layer material, so that the protective layer has high damage resistance. When the initial wafer has not been degraded or damaged, it can be put into the furnace tube or reaction chamber multiple times. Indoor, used for monitoring wafers and/or filling wafers. In this way, the auxiliary wafer can be recycled with a higher number of times, and the use cost of the control wafer (Control Wafer) and/or the dummy wafer (Dummy Wafer) can be effectively reduced.

Correspondingly, an embodiment of the present application also provides a semiconductor manufacturing process for applying the above-mentioned auxiliary wafer.

Referring to FIG. 3, a product wafer 210 and the aforementioned auxiliary wafer 220 are provided. The product wafer 210 and the auxiliary wafer 220 are placed in the furnace tube 200 to prepare for the same manufacturing process to form the same required functional layer.

Referring to FIG. 4, Step A: Perform the same manufacturing process on the product wafer 210 and the auxiliary wafer 220. The manufacturing process includes deposition, etching, annealing, and printing to form a functional layer on the surface of the product wafer 210 and the auxiliary wafer 220 230.

In this embodiment, the product wafer 210 and the auxiliary wafer 220 have the same size; in other embodiments, the initial wafer size in the auxiliary wafer is the same as the product wafer size.

In this embodiment, after the functional layer 230 is formed, at least one auxiliary wafer 220 is taken out of the furnace tube, or at least one auxiliary wafer 220 is taken out of the reaction chamber, and the functional layer 230 above the auxiliary wafer 220 is measured. Thickness, so as to preliminarily determine whether the functional layer 230 meets the preset requirements. If the requirement is met, the functional layer 230 on the surface of the auxiliary wafer 220 is removed; if the requirement is not met, the defect type and the cause of the defect are analyzed based on the functional layer 230 on the surface of the auxiliary wafer 220.

In addition, after the thickness of the functional layer 230 meets the preset requirements, the functional layer 230 may be further subjected to performance testing, such as electrical performance testing; if the performance of the functional layer 230 meets the preset requirements, the functional layer 230 is removed.

Step B: Remove the functional layer 230 on the surface of the auxiliary wafer 220.

The functional layer 230 is usually removed by a mixture of HF/HNO3 to ensure that the functional layer 230 can be completely removed. Since α-AL2O3 is extremely stable to acid, resistant to corrosion by HF/HNO3 mixture, and has high hardness, the damage caused by a single removal process to α-AL2O3 is limited, and the damage does not affect the auxiliary wafer In the case of 220 performance, the remaining auxiliary wafer 220 can be recycled. That is to say, in the semiconductor manufacturing process, the above steps A and B can be performed cyclically until the performance of the auxiliary wafer 220 does not meet the requirements, and the performance does not meet the requirements refers to the performance of either the protective layer or the initial wafer. Then meet the process requirements.

According to the test results, the 2nm-thick α-AL2O3 can withstand the damage of about 300 times of the removal process, and its performance is greatly improved compared with the existing protective layer.

In this embodiment, a semiconductor manufacturing process is provided, and the above-mentioned auxiliary wafer is applied in the semiconductor manufacturing process, so that the auxiliary wafer can be recycled for multiple times, and the process cost is reduced.

Those of ordinary skill in the art can understand that the above-mentioned embodiments are specific examples for realizing the present application, and in actual applications, various changes can be made to them in form and details without departing from the spirit and spirit of the present application. Scope. Any person skilled in the art can make their own changes and modifications without departing from the spirit and scope of this application. Therefore, the protection scope of this application shall be subject to the scope defined by the claims.

Claims

A method for forming an auxiliary wafer includes:

Provide initial wafers;

Forming a protective film on the surface of the initial wafer, the material of the protective film includes low-temperature phase alumina;

An annealing process is performed on the protective film, so that at least part of the aluminum oxide is transformed from the low-temperature phase to the high-temperature phase to form a protective layer.
The method of claim 1, wherein the forming a protective film on the surface of the initial wafer comprises: using a precursor to form the protective film on the surface of the initial wafer, and the precursor includes Base aluminum and ozone, or, the precursor includes aluminum trichloride and ozone.
The forming method according to claim 2, wherein a carrier gas is used to carry the trimethylaluminum, and the flow rate of the carrier gas is 100 sccm to 400 sccm.
The forming method according to claim 2, wherein the protective film is formed using the precursor under a temperature condition of 200°C to 600°C.
The forming method according to claim 1, wherein the annealing process includes spike annealing, and the annealing temperature of the spike annealing is greater than 900°C.
The forming method according to claim 1, wherein the high-temperature phase alumina includes α-alumina.
The forming method according to claim 1, further comprising: forming a functional layer on the protective layer, and the etching selection ratio of the functional layer and the initial wafer in the same etching process is smaller than that of the functional layer. The etching selection ratio of the layer to the protective layer.
An auxiliary wafer including:

The initial wafer and the protective layer on the surface of the initial wafer, the material of the protective layer includes alumina, and the phase of the alumina includes a high-temperature phase.
8. The auxiliary wafer according to claim 8, wherein the thickness of the protective layer is greater than or equal to 2 nm in a direction perpendicular to the surface of the initial wafer.
The auxiliary wafer according to claim 8, wherein the material of the protective layer includes α-alumina.
A semiconductor manufacturing process, including:

Provide product wafers and auxiliary wafers according to any one of claims 8 to 10;

Step A: Perform the same manufacturing process on the product wafer and the auxiliary wafer to form a functional layer on the surface of the product wafer and the auxiliary wafer;

Step B: Remove the functional layer on the surface of the auxiliary wafer.
The semiconductor manufacturing process according to claim 11, wherein said step A and said step B are performed cyclically.